In the building industry there are many applications in which a load bearing member, such as a truss or beam, is required which is light in weight and has the ability to support large loads over long, clear spans. Trusses of various shapes and sizes are typically used to support the floor and roof of multi-story buildings, such as residential apartments and office buildings. A truss is typically comprised of a top chord and a bottom chord, which may be mutually parallel or inclined with respect to one another, depending upon the type of the truss. For example, in a flat truss, which is used to support a floor, the top and bottom chords are disposed in parallel relationship. In a cantilever or vaulted scissors truss, which is used to support the roof of a building, the top chord is inclined with respect to the bottom chord and is comprised of two chord members which intersect at the apex of the truss. The top and bottom chords are typically co-planar and are interconnected by means of metal or wooden webs, which extend diagonally between the top and bottom chords. Beams of various sizes and shapes are also used for structural support. A beam is typically comprised of top and bottom flanges interconnected by a web member, which may be a sheet of plywood or the like.
In order for a support structure to be commercially viable, it must achieve the required fire resistance rating for the particular support structure. Standard fire resistance tests are used to rate and compare load bearing structures, such as trusses and beams, which are used in the construction of buildings. The test measures the ability of a support structure to resist failure for a particular period of time when subjected to the standard fire exposure conditions prescribed by the test. Failure can occur either when flames, hot gasses or excessive heat escapes from the test assembly or when there is a structural collapse of the assembly. Unprotected wooden trusses and beams may not be able to achieve the required fire resistance ratings, thereby necessitating the application of fire protective materials to the support structures to enhance their fire resistance.